In the related art, a device configured to transmit a rotating force by a magnetic coupling is proposed (Patent Document 1, FIG. 2(c)).
In the above described Patent Document, a mechanism which transmits a rotating force efficiently by magnetic attracting forces of a number of magnetic poles is proposed. However, when a load torque exceeding a magnetic coupling force is applied to the torque transmission device, idle running is resulted. However, in order to detect the presence or absence of the idling, a complicated detecting mechanism is required for detecting the difference in rotation between two rotating bodies.
A non-contact load-sensing automatic transmission configured to perform a switching operation of a magnetic clutch magnetically according to the load is also proposed (Patent Document 2).
The non-contact load-sensing automatic transmission includes input means from a decelerator, a rotating body rotatably coupled to the input means, magnetic bodies fixed to the rotating body with positions of axial directions shifted from each other, a speed switching member including a magnet for a magnetic clutch which is capable of opposing the respective magnetic bodies via a gap and provided so as to be movable in the axial direction and a rotation-thrust converting mechanism configured to change the relative position in the direction of rotation with the speed switching member according to a load applied to an output side and to move the speed switching member in the axial direction by the change of the relative position in the direction of rotation, wherein the rotation-thrust conversion mechanism is configured to change the speed of the output means by switching repulsive and attractive operations between a magnet provided on the speed switching member and a magnet provided on an output side member on the basis of the change in relative position in the direction of rotation according to the load, and moving the speed switching member in the axial direction by the switching to cause the magnet for the magnetic clutch to oppose any one of the magnetic bodies of the rotating body. Therefore, the structure is complicated, the switching operation is unstable, and downsizing is difficult.
Patent Document 1: JP-A-57-134066
Patent Document 2: JP-A-2004-347027